Codeforces Round #329 (Div. 2) D. Happy Tree Party

Myth丶恋晨 2022-08-10 00:53 17阅读 0赞

对于从a→b 的路径，如果边权值为1，则值不变，否则就是1≤边权值，这样的话最多除64次就为0也就不需要继续除下去了，所以问题的关键在于去压缩哪些连续的边权为1的路径，这里自然就想到并查集啦，具体实现看代码吧！  
另：因为更改后的边权值只会变小，所以只会涉及到集合并和查的操作。这一点要想懂。

// whn6325689
    // Mr.Phoebe
    // http://blog.csdn.net/u013007900
    #include <algorithm>
    #include <iostream>
    #include <iomanip>
    #include <cstring>
    #include <climits>
    #include <complex>
    #include <fstream>
    #include <cassert>
    #include <cstdio>
    #include <bitset>
    #include <vector>
    #include <deque>
    #include <queue>
    #include <stack>
    #include <ctime>
    #include <set>
    #include <map>
    #include <cmath>
    #include <functional>
    #include <numeric>
    #pragma comment(linker, "/STACK:1024000000,1024000000")
    
    
    using namespace std;
    #define eps 1e-9
    #define PI acos(-1.0)
    #define INF 0x3f3f3f3f
    #define LLINF 1LL<<50
    #define speed std::ios::sync_with_stdio(false);
    
    typedef long long ll;
    typedef unsigned long long ull;
    typedef long double ld;
    typedef pair<ll, ll> pll;
    typedef complex<ld> point;
    typedef pair<int, int> pii;
    typedef pair<pii, int> piii;
    typedef vector<int> vi;
    
    #define CLR(x,y) memset(x,y,sizeof(x))
    #define CPY(x,y) memcpy(x,y,sizeof(x))
    #define clr(a,x,size) memset(a,x,sizeof(a[0])*(size))
    #define cpy(a,x,size) memcpy(a,x,sizeof(a[0])*(size))
    #define debug(a) cout << #a" = " << (a) << endl;
    #define debugarry(a, n) for (int i = 0; i < (n); i++) { cout << #a"[" << i << "] = " << (a)[i] << endl; }
    
    #define mp(x,y) make_pair(x,y)
    #define pb(x) push_back(x)
    #define lowbit(x) (x&(-x))
    
    #define MID(x,y) (x+((y-x)>>1))
    #define getidx(l,r) (l+r | l!=r)
    #define ls getidx(l,mid)
    #define rs getidx(mid+1,r)
    #define lson l,mid
    #define rson mid+1,r
    
    template<class T>
    inline bool read(T &n)
    {
        T x = 0, tmp = 1;
        char c = getchar();
        while((c < '0' || c > '9') && c != '-' && c != EOF) c = getchar();
        if(c == EOF) return false;
        if(c == '-') c = getchar(), tmp = -1;
        while(c >= '0' && c <= '9') x *= 10, x += (c - '0'),c = getchar();
        n = x*tmp;
        return true;
    }
    template <class T>
    inline void write(T n)
    {
        if(n < 0)
        {
            putchar('-');
            n = -n;
        }
        int len = 0,data[20];
        while(n)
        {
            data[len++] = n%10;
            n /= 10;
        }
        if(!len) data[len++] = 0;
        while(len--) putchar(data[len]+48);
    }
    //-----------------------------------
    
    const int MAXN = 10+2e5;
    
    int n, m;
    int dep[MAXN], st[MAXN];
    ll w[MAXN];
    vector<pii> g[MAXN];
    pii pre[MAXN];
    
    void dfs(int u,int fa)
    {
        dep[u] = dep[fa]+1;
        for(auto it:g[u])
        {
            int v = it.first;
            int id = it.second;
            if(v == fa) continue;
            pre[v] = mp(u,id);
            dfs(v,u);
        }
    }
    int find_set(int u)
    {
        if(w[pre[u].second] != 1) return u;
        if(st[u] == u)
            return st[u] = find_set(pre[u].first);
        return st[u] = find_set(st[u]);
    }
    int jmp(int a,ll &v)
    {
        int id = pre[a].second;
        if(w[id] > 1)
        {
            v /= w[id];
            return pre[a].first;
        }
        return st[a] = find_set(st[a]);
    }
    ll cal(int a,int b,ll v)
    {
        while(v && a!=b)
        {
            if(dep[a] < dep[b]) swap(a,b);
            a = jmp(a,v);
        }
        return v;
    }
    int main()
    {
        // freopen("in.txt","r",stdin);
        scanf("%d%d",&n, &m);
        for(int i = 1; i < n; i ++)
        {
            int u,v;
            scanf("%d%d%I64d",&u,&v,&w[i]);
            g[u].pb(mp(v,i)), g[v].pb(mp(u,i));
        }
        dfs(1,0);
        for(int i = 1; i <= n; i ++) st[i] = i;
        while(m --)
        {
            int tp;
            scanf("%d",&tp);
            if(tp == 1)
            {
                int a, b;
                ll y;
                scanf("%d%d%I64d",&a, &b, &y);
                printf("%I64d\n",cal(a,b,y));
            }
            else
            {
                int p;
                ll c;
                scanf("%d%I64d",&p, &c);
                w[p] = c;
            }
        }
        return 0;
    }